x^2+9x=-16

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Solution for x^2+9x=-16 equation:


Simplifying
x2 + 9x = -16

Reorder the terms:
9x + x2 = -16

Solving
9x + x2 = -16

Solving for variable 'x'.

Reorder the terms:
16 + 9x + x2 = -16 + 16

Combine like terms: -16 + 16 = 0
16 + 9x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-16' to each side of the equation.
16 + 9x + -16 + x2 = 0 + -16

Reorder the terms:
16 + -16 + 9x + x2 = 0 + -16

Combine like terms: 16 + -16 = 0
0 + 9x + x2 = 0 + -16
9x + x2 = 0 + -16

Combine like terms: 0 + -16 = -16
9x + x2 = -16

The x term is 9x.  Take half its coefficient (4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
9x + 20.25 + x2 = -16 + 20.25

Reorder the terms:
20.25 + 9x + x2 = -16 + 20.25

Combine like terms: -16 + 20.25 = 4.25
20.25 + 9x + x2 = 4.25

Factor a perfect square on the left side:
(x + 4.5)(x + 4.5) = 4.25

Calculate the square root of the right side: 2.061552813

Break this problem into two subproblems by setting 
(x + 4.5) equal to 2.061552813 and -2.061552813.

Subproblem 1

x + 4.5 = 2.061552813 Simplifying x + 4.5 = 2.061552813 Reorder the terms: 4.5 + x = 2.061552813 Solving 4.5 + x = 2.061552813 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x = 2.061552813 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = 2.061552813 + -4.5 x = 2.061552813 + -4.5 Combine like terms: 2.061552813 + -4.5 = -2.438447187 x = -2.438447187 Simplifying x = -2.438447187

Subproblem 2

x + 4.5 = -2.061552813 Simplifying x + 4.5 = -2.061552813 Reorder the terms: 4.5 + x = -2.061552813 Solving 4.5 + x = -2.061552813 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x = -2.061552813 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = -2.061552813 + -4.5 x = -2.061552813 + -4.5 Combine like terms: -2.061552813 + -4.5 = -6.561552813 x = -6.561552813 Simplifying x = -6.561552813

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-2.438447187, -6.561552813}

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